Field of Invention
The invention relates to a method for adjusting the azimuth of a wind power plant, in which, during an azimuthal rotation of a machine housing with a rotor on a tower of the wind power plant, a constant residual pressure for generating a constant residual holding torque is applied to at least one azimuth braking device. The invention also relates to an azimuth adjustment system for a wind power plant and to a wind power plant.
Brief Description of Related Art
The azimuth adjustment system of a wind power plant has the function of rotating the machine housing with the rotor on the tower into the wind again, that is to say of adjusting its azimuth position or the azimuth angle, during operation of a wind power plant when the wind direction changes beyond a predeterminable amount. A further object is to move the azimuth position of the machine housing or of the gondola of the wind power plant in order to untwist the cables, which lead from the machine housing into the tower, if the machine housing has been moved in one direction to such an extent that maximum permissible twisting of the cables has taken place. Finally, the azimuth angle of the machine housing can also be moved with the rotor, in order to set a predetermined position, for example for maintenance work, when the wind power plant is stationary, which predetermined position is desired, for example, for the approach of a helicopter, in particular in offshore wind power plants.
In order to adjust the machine housing or the gondola with the rotor in its azimuth position, the wind power plant has one or more azimuth drives which usually each have a motor or two motors with a gear mechanism which is connected downstream and has a gearwheel or gearwheels which engage or engages in a corresponding crown gear on the tower, or vice versa. In addition, the azimuth adjustment system has at least one azimuth braking device, for example with brake calipers, which act on a brake disk. Said brake calipers serve to lock the machine housing in the adopted azimuth position, after the azimuth adjustment has ended, with the result that the azimuth adjustment drives are no longer loaded.
The azimuth braking devices also have a function during an azimuth adjustment process. A residual pressure is usually applied to them in order to generate a residual holding torque. Said residual holding torque serves to decouple the azimuth drives from external interference influences which occur, for example, as a result of the fact that gusts of wind act on the rotor of the wind power plant and exert an azimuthal torque on the machine housing. Without the residual holding torque applied by the azimuth braking devices, the azimuthal torque would be conducted directly onto the azimuth drives, which would as a result adversely affect them in terms of their function and their service life.
DE 10 2008 004 948 A1 discloses a method for rotating a machine housing of a wind power plant by moving an azimuth adjustment device, in which method, during the movement of the azimuth adjustment device by means of a braking device, a residual holding torque which brakes the azimuth adjustment device is maintained. In this case, during the movement of the azimuth adjustment device a rotational speed and/or a torque of an azimuth drive of the azimuth adjustment device are measured, and in the case of a deviation of the measured parameter from a setpoint value the magnitude of the holding torque exerted by the braking device is regulated in such a way that the at least one operating parameter is approximated again to the setpoint value. In this way, rotational speed fluctuations of the azimuth drive which occur are reduced. The entire contents of the disclosure in DE 10 2008 004 948 A1 are to be incorporated into the present patent application by reference.
The method which is specified therein constitutes a regulating process with which the motors of the azimuth adjustment device operate particularly constantly, since wind influences which assist or impair the azimuth adjustment are compensated by increasing or reducing the residual holding torque. It is disadvantageous here that the measurement is very susceptible to faults because the sensor can fail and the regulating speed of the regulating circuit can be an impediment, starting from the measured motor rotational speed or the torque of the azimuth adjustment device via the change in the residual holding torque as far as the associated change in the rotational speed or the torque of the azimuth drive. The corresponding azimuth drives also have to be regulated in terms of their rotational speed, and the control of the controller as well as a variable application of pressure for the brake calipers of the azimuth braking device are comparatively costly.
In contrast, the present invention is based on the object of making available a method, an azimuth adjustment system and a wind power plant in which azimuth adjustments can be implemented cost effectively and with a high level of operational reliability and little wear on azimuth braking calipers or azimuth braking devices.